名词性从句
陈述语序
主语从句What I say is true
宾语从句He won’t believe what I say.
表语从句That is what I said.
同位语从句I told them the news that Rockets won the game today.
区别什么从句应看主句，主句不完整时从句肯定是名词性从句。主句完整时，从句可能是定语从句，状语从句，或者同位语从句。
I have forgotten where we went yesterday.
Where we went yesterday is covered with all kinds of flowers.
Oh! This is where we came yesterday.
This is the place where we came yesterday.
Here, he made the promise that he would come here 10 years later.
I will make a mark where he made the promise.
需要用什么引导词看从句。名词性从句中缺什么意思用什么意思的引导词; 缺名词性成份时，指人用who/whom，指物用what; 不缺意思和成份时用that。That 只有在宾语从句中可以省略。
1. ___ the Olympic Games will be held in Beijing is known.
A.不填 B. Whenever C. What D. When
2. There is a common belief among them ___ rubbish can and should be put to good use.
A. which B. if C. whether D. that
3. He’s bought a cottage for ___ he retires, with the money he saved.
A. When B. where C. what D. which (哪一个、哪一些)
--It is known to all that Taiwan belongs to China.
--Do you think it possible that we take over Taiwan?
--Of course.
It 经常在句中当形式主语、宾语，代替真正的主语、宾语，以避免头重脚轻。
It is pretty well understood ___ controls the flow of carbon dioxide in and out of the atmosphere today.
A. That B. when C. what D. how
Why don’t you bring ___ to his attention that you are too busy to do it?
A. This B. what C. that D. it
表“是否”时只用whether不用if:
1. Whether the president will come is not known yet. (主从)
2. The problem is whether we need it.(表从)
3. The problem whether we will build another school hasn’t been settled.
(同位语从句)
4. He was worried about whether he passed the English examination. (介词之后)
5. It doesn’t matter whether she will come or not. (whether… or /or not)
I don’t know whether to go.(动词不定式之前)
